Recently, computer use has greatly increased. In order to share information between a plurality of computers, networks are used to connect computers; for example, Ether-Net is generally used as the transmission structure between computers. Generally speaking, the transmission mode of Ether-Net is a type of asynchronous transmission, and the transmission medium used in this network is coaxial cables. Since asynchronous serial transmission is used, the working frequency of transmitter must be the same as that the receiver, so as to ensure correction of data transmission. A data sampling method has been used in some applications, in which the transmission data is sampled by a sampling clock at a frequency that is higher than that of the Recovered Clock RXC in the protocol. Usually the sampling clock frequency is 16 times that of the Recovered Clock RXC. Since asynchronous transmission data has a start bit, the receiver repeatedly reads transmission data levels at the sampling clock, which is defined as the reference frequency. Once the start bit is detected, then the receiver will read data by using a receiving frequency. Usually, the Transmitting Clock TXC and Recovered Clock RXC frequency are determined in the protocol and are generated from the oscillators of the transmitter and receiver, respectively. But because the electronic circuitry and transmission medium may be interfered with so that the Transmitting Clock TXC of the transmitter and the Recovered Clock RXC of the receiver are not matched, causing some errors in the data read on the receiver, thus reducing the reliability of the network.